Male whales woo with lovesongs

The low-frequency, repetitive booming calls of fin and blue whales – some of the loudest songs in the oceans – are male lovesongs, say US researchers.

The team has shown that only males produce these vocalisations, leading them to conclude that they must be songs used for breeding purposes.

“Previously, it was thought that whales might use their song as a long-wave sonar to detect obstructions and orientate themselves by echoes bouncing off islands and under-water canyons.

“This research suggests that the songs are used for breeding purposes – to attract females or ward off other males – since only males produce them,” says Vincent Yanik, a vocalisations expert at the Sea Mammal Research Unit at St Andrews University.

Scientists at the University of California, Santa Cruz, and colleagues towed hydrophones and sound-localisation equipment from boats near fin whales to determine which individual was producing the sound. They then took small skin samples of the singing whales to determine their gender – only the males made the loud, low frequency songs.

Human interference

“If you compare the whales to other species, like birds, in cases where only males sing, the females use the repertoire size as a correlation to genetic quality of the male. Fin and blue whales often sing for days and the females may be swimming round them to decide which has the largest repertoire,” says Yanik.

“But they may, like cormorants, be using their song as an aggressive warning to keep male rivals at bay. Studies have shown that individual humpback whales that sing swim much further apart than those that do not – and the females show no interest in their songs,” Yanik told New Scientist.

The researchers hope their study will help focus research on the effect of the high levels of human-produced sound from commercial ships, military sonar and seismic research, which are increasingly in the frequency range used by large whales.

“Fin and blue whale songs carry for hundreds of kilometres so it’s easy for a female to stay in range, but man-produced low-frequency emissions can cause transmission breakdown, so the female cannot hear the male even if she is just 50 metres away.

“This could have the effect of cutting down the encounter rate between whale, which is a serious problem – they only produce calves every three or four years,” Yanik said.